In mobile vehicles, particularly in work machines such as wheel loaders, there is a need to obtain sufficient power for the hydraulic system even when the service brake is actuated and thus the driving speed is low.
In work machines such as wheel loaders, on one hand, a driving motor drives the driving wheels via a hydrodynamic torque converter and a clutch device and, on the other hand, drives the power-consuming devices, such as hydraulic pumps which, for example, the loading shovel of the wheel loader is operated. Wheel loaders comprise a control function, as a result of which, at the beginning of the loading operation, the driving clutch is opened upon actuation of the service brake, this acts upon the vehicle wheels by disconnecting the hydraulic actuating pressure in a hydraulic, actuated clutch element. As a result of the opening of the driving clutch, the engine power is available almost exclusively to the vehicle hydraulic system for actuating the piston/cylinder arrangement of the loading shovel. Above all, this is associated with the fact that without this control function a very high power loss develops in the torque converter when the drive is connected and the vehicle service brake is actuated, since the turbine wheel in the converter has come to a complete or nearly complete halt, while the pump wheel, driven by the driving motor, rotates at the stall speed.
DE 102 30 993 A1 describes a method for controlling functions of an occupational vehicle, where a driving motor drives vehicle wheels via a driving clutch, and a service brake acts upon the vehicle wheels, and the driving motor drives a hydraulic pump, with the driving clutch between the driving motor and the driving wheels being automatically opened and the service brake being automatically closed when the load acting upon the driving device of the vehicle, for example the weight of the loader shovel, exceeds a predefined load threshold or is actuated such that DE 102 30 993 A1 describes a method for controlling functions of an occupational vehicle, where a driving motor drives vehicle wheels, via a driving clutch; a service brake acts upon the vehicle wheels, and the driving motor drives a hydraulic pump with the driving clutch between the driving motor and the driving wheels is automatically opened. The service brake is automatically closed when the load acting upon the driving device of the vehicle, for example, the weight of the loader shovel, exceeds a predefined load threshold or is actuated such that it exceeds this threshold. A wheel loader, however, may encounter a plurality of driving situations in which it is not always desirable to automatically open the service brake and the clutch device with an exceeding load on the working device. For example, if the wheel loader travels up a ramp to the unloading site when feeding a crushing or sorting system, there is a possibility that the wheel loader is slowed down upon actuating the working device, although it has not yet assumed the final position. In the same way, based on the level of dexterity, there is also the possibility that the clutch device is opened when the automatic system is not used, while the service brake has not yet been sufficiently closed resulting in the vehicle rolling down the ramp.
It is the object of the present invention to create a device for controlling the functions of a mobile vehicle and a method for controlling these functions in which a clutch device, which is set between the driving motor and the vehicle wheels, can be opened in order to supply the power-consuming devices with sufficient power and thereby to take the different driving situations of the vehicle into consideration.